I’ve been thinking lately about stereotypes, and how it’s so easy to fall into using them, even when I try to stay on moral high ground. As a writer, it could even be said that I depend on them. If, say, I were to write, “The thin black man put a hand to his cheek and drew his fingers through a patchy beard. His nails were long and covered with what looked like motor oil,” I’m willing to bet you could envision the person. He would not be dressed in a suit.

The trick is to avoid snap judgments and prejudices based on appearance, class or race.

Stereotypes, I think, are used most poisonously against the world’s poor. Here’s one that’s common in the U.S.: The rich are smarter than the poor. If that weren’t the case, the poor would simply make better choices and improve their life circumstances. That stereotype has a close cousin: The poor are lazy. If that weren’t the case . . .

You get the idea.

I’m dismayed by how frequently I judge poor people, based on those kinds of stereotypes. This happened just recently, when I met someone who was struggling to pay her mortgage and health insurance. She was worried about losing her home. In addition to two children, she has three dogs.

“What???” I wanted to shout. “Are you crazy? Don’t you know how expensive it is to keep a dog?”

I managed to say nothing. And as soon as I got home, I went to my bookshelf and got out my copy of a wonderful book called Poor Economics, by Abhijit Banerjee and Esther Duflo.

Banerjee and Duflo are faculty members at the Massachusetts Institute of Technology. They’ve founded a network of researchers who study poverty alleviation techniques. The subtitle for their book is A Radical Rethinking of the Way to Fight Global Poverty, and their web site opens with these questions:

Why would a man in Morocco who doesn’t have enough to eat buy a television? Why is it so hard for children in poor areas to learn even when they attend school? Why do the poorest people in the Indian state of Maharashtra spend 7 percent of their income on sugar?

There are valid answers to all these questions, and Banerjee and Duflo have staked their careers on finding them. Here, in brief, are some of their conclusions:

Studies and interviews have repeatedly shown that when hungry people get a little extra money, they don’t spend it on increased amounts of food. It’s more likely they’ll buy a different, more expensive kind of food to break the boredom of their meager meals. In some societies they might use the windfall for a more lavish wedding or funeral, because honoring loved ones is more important than the temporary satisfaction that comes from a full belly. Or they’ll get a pet they can cuddle and love. Sometimes they’ll choose to purchase a television, DVD player, or stereo. In an existence with little daily variety and so few opportunities, losing themselves in someone else’s stories can be a powerful balm.

I’ve long thought that the poor would be well advised to save every extra cent in hopes of bettering themselves. But, Banerjee and Duflo write, consider the amount of will power that financially stable people bring to their New Year’s resolutions. Year after year our resolutions are quickly broken. We know we should exercise, eat right, save more money, and so on, but things keep getting in the way. The poor do the same. We’re all only human. The rich make bad decisions all the time. But we have the resources to buffer ourselves from the consequences.

The poor exist in a state of worry and stress unknown to those of us leading comfortable lives, Banerjee and Duflo point out. This carries its own set of consequences, among them an elevated presence of cortisol in the brain. Cortisol can impair cognitive ability. “When experimental subjects are artificially put under stressful conditions in the laboratory, they are less likely to make the economically rational decision when faced with choosing among different alternatives,” they write.

The extremely poor often live in a numbed state, moving dully from crisis to crisis, showing little emotion, accepting their lot with a dull resignation that can be infuriating to those trying to help them. What you see is not who they truly are. “There is so much risk in the everyday life of the poor,” Duflo and Banerjee write, “that somewhat paradoxically, events that are perceived as cataclysmic in rich countries barely seem to register with them.”

Reading this again, I was very glad I hadn’t yelled at the struggling woman with the three dogs. She likely needs much more than a lesson on sticking to a budget, though that might be helpful. In her case, as with so many people, finding long-term solutions will be a lengthy process, with no simple answers.

Here’s a link to the web site for Poor Economics, which has been praised by both liberal and conservative reviewers. Give it a look.